Metal extrusion machine



June 18, 1940. 1', w, VE 2,204,961 v METAL EXTRUSION MACHINE Filed June22, 1938 6 Sheets-Sheet 1 BYE "MM ,June 18, 1940.

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METAL EXTRUSION MACHINE Filed June 22. 1938 Fig. 2.

6 Sheets-Sheet 2 MMrm June 18, 1940. w, GR|EVE 2,204,961

METAL EXTRUSION MACHINE Filed June 22, 1938 6 Sheets-Sheet 3 a ze saATTOF/VEYS June 18, 1940.

G. T. W. GRIEVE METAL EXTRUSION MACHINE 6 Sheets-Sheet 4 Filed June 22,1938 65cm Tim-us Wusav Ge/EYA' June 18, 1940. e. 'r. w. GRIEVE METALEXTRUSION MACHINE Filed June 22, 1938 6 Sheets-Sheet 5 mm B we ww Aw NME m/vf/vm? 65am: 70am: Vase/v ems-v5 June 18, 1940. G. T. w. GRIEVEMETAL EXTRUSION MACHINE Filed June 22, 1938 6 Sheets-Sheet 6 Ge'awas77/0 gm. wrf w u Patented June 18, 1940 UNITED STATES ATENT OFFICE METALEXTRUSION MACHINE George Thomas Wilson Grieve, Woolwich,

London, England, assignor to Henley Extrusio Machine Company Limited,London,-England,

a. British company 24 Claims.

This invention relates to continuous metal extrusion machines of thekind in which plastic metal is driven into an extrusion chamber andthence through an extrusion orifice by a rotating screw-threadedimpelling device which comprises an inner member and a tubular, thoughnot necessarily cylindrical, outer member, and of which the axis ishorizontal or is inclined at a small angle to the horizontal. Such amachine will hereinafter be referred to as a horizontal metal extrusionmachine of cylindrical type to distinguish it from extrusion machineshaving a vertical axis and also from extrusion machines with'animpelling device of disc form. In horizontal metal extrusion machines ofcylindrical type a drive is applied to the rotatable part of theimpelling device at a point to the rear of the extrusion chamber. Forthis purpose an opening is provided in the lower part of the extrusionmachine casing of which a part, instead of merely housing the impellingdevice, may in some cases actually constitute the outer member of theimpelling device. Generally the apertured part of the casing issurrounded by a downwardly extending wall forming a hollow pedestalsupport for the machine and serving as a housing for a gear drive to therotatable part of the impelling device. In such machines heavy thrustloads are exerted by the plastic metal on the front Wall of theextrusion chamber and on the stationary and rotating parts of theimpelling device, the load on the rotating member having to be taken upby a large thrust bearing. These loads result in the casing beingsubjected to heavy tensile stresses in a longitudinal direction.

1 It has been found that the casings of such machines unless heavilyreinforced by the addition of special strengthening members in theneighbourhood of the apertured part of the casing, distort under theheavy thrust loads exerted upon them to such an extent that, in the caseof machines of the kind in which the concentric members constituting theimpelling device are not relatively supported at their front ends, thesemembers are caused to assume a non-parallel position. When inner andouter dies are used this results in that the inner die or point is nolonger concentric with the outer die or matrix, and the product, insteadof having a uniform Wall thickness, has a Wall that is thicker on theupper side than on the lower side of the product as it leaves themachine. In cases where supports extending between the relativelyrotating concentric members forming the impelling device are provided atthe delivery end of the device, distortion of the casing producesabnormal wear on the supporting surfaces and eventually eccentricity ofthe point and matrix. It is an object of this invention to provide animroved construction of horizontal extrusion machine of the cylindricaltype which avoids the possibility of distortion of the casing under thethrust loads to which it is subjected Without the necessity forproviding special strengthening members.

It has been found that casings of horizontal extrusion machines of thecylindrical type as at present constructed also distort due totemperature differences in the various parts of the casing. Generallythe underneath part of the easing in the region of the supportingpedestal will be cooler than the upper part. The consequent unequalexpansion of these parts of the casing will result in distortion of thecasing, and hence in eccentricity of the parts of the impelling deviceand of the dies or in abnormal wear of the supporting surfaces providedto maintain the parts concentric. This eccentricity will generally be inthe reverse direction to that due to the thrust load but the two effectswill not counterbalance one another. Unequal cooling of different partsof the casing also leads to unequal cooling of the plastic metal atdifferent parts of the circumference. Generally the effect of this is toincrease the rate of extrusion in one side of the impelling device. Thisis naturally disadvantageous, and may lead to eccentricity of the partsof the impelling device and to imperfections in the extruded product. Itis a further object of the present invention to provide an improved formof construction which avoids such temperature differences and ensuresthat the casing expands symmetrically thus eliminating the possibilityof its distortion,

In our improved form of construction of extrusion machine of the screwthread impeller type, the parts of the casing which houses the impellingdevice and the driving wheel thereof and which are subjected to thethrust loads exerted by the plastic metal are made symmetrical about theaxis of the impelling device and, preferably, also symmetrical insection in any plane containing the said axis. By the term symmetricalwe mean symmetrical apart from minor apertures such as bolt holes, oilchannels and the like, in other words, that the general form of the partof the casing subjected to thrust loads is symmetrical. The effect ofthis is that the extension or compression of the casing due to thethrust load exerted upon it is equal at all diametrically oppositepoints so that no eccentric distortion thereof takes place and hence noeccentric displacement of the impelling parts and dies nor excessivewear of the guide surface or surfaces (if any) supporting the front endof the members constituting the impelling device.

Where the part of the casing in the vicinity of the supports is notsubjected to thrust loads exerted by the plastic metal, it isnotessential, from the point of view of avoiding distortion due to thrustloads, for it to be symmetrical but it is preferably made so to avoiddistortion due to thermal stresses and asymmetrical driving stresses,and to avoid unequal extrusion at different parts of the circumference.This preferred form of construction will generally necessitate theprovision of separate supporting mernbers. These are preferably heatinsulated from the casing. The symmetrical form of construction willalso necessitate a modified form of drive as compared with the formsthat have been proposed or used for machines of this kind.

By way of example the invention will be further described with referenceto the accompanying drawings wherein,

Figure 1 is a longitudinal section, taken on the line I! in Figure 2,through one form of extrusion machine constructed in accordance with theinvention,

Figure 2 is a front end elevation of the machine shown in section inFigure 1,

Figure 3 is a side view partly in longitudinal section and partly inelevation of a modified form of extrusion machine constructed inaccordance with the invention,

Figure 4 is a rear end elevation of the machine shown in Figure 3.

Figure 5 is a fragmental View, partly in section On the line V-V inFigure 4 and partly in elevation looking in the direction of arrow X inFigure 4, of the machine shown in Figures 3 and 4,

Figure 6 is a fragmentary cross-section showing a modified form of thecoupling between the machine casing and the gear casing shown in Figure3,

Figure 7 is a plan view, partly in section on the line VII-VII in Figure8 of a second type of extrusion machine constructed in accordance withthe invention,

Figure 8 is a rear end elevation of the machine shown in Figure '7, and

Figure 9 is a fragmental cross-section taken on the line IXIX of Figure8.

The machine shown in Figures 1 and 2 of the drawings will first bedescribed. It comprises a rotatable tubular member I which works in acylindrical casing 2a and has on its outer surface helically extendingprojections 3 which cooperate with longitudinally extending projections4 on the adjacent inner surface of the casing to form a screw threadmetal impelling device. The front end wall 5 of the casing is furnishedwith an extrusion die or matrix 6 and an inner die or point I,co-operating with the matrix to form an annular extrusion orifice, ismounted on the end of a stationary tubular member 8 which passesco-axially through the rotating tubular member l. Metal in a moltenstate is fed into the space between the casing and the rotating tubularmember through the inlet passage 9 and is cooled sufficiently toco-operate with the projections 3 and i by which it is moved forward ina plastic condition into the extrusion chamber I and out through theextrusion orifice. I-Ielically extending projections 30. andlongitudinally extending projections ta are also provided on the innersurface of the rotating member and on the adjacent outer surface of thetubular member 8, respectively, to constitute an auxiliary screw threadimpelling device which is supplied with molten metal through ports 9a inthe rotating member I. An example of a machine of this type is describedin the specification of British Patent No. 430,006. Hitherto thestationary member 8 has been supported from the rear wall of the machinecasing 2 and the thrust on the rotating tube I has been taken up by therear wall of the casing through a ball thrust bearing disposed betweenthe rear wall and. an abutment on the rear end of the tube, and the tubehas been driven by a wheel mounted on the rear end thereof to whichadrive was applied through an aperture in the bottom of the casing bygear wheels housed in a hollow pedestal supporting the casing. With thisconstruction the machine casing is subjected to tension throughout itslength due to the thrust loads. In the improved construction shown inFigures 1 and 2, there is provided on the wall of the machine casing aninwardly extending flange H which is located in front of a driving wheelI2 mounted on the rear end of the rotating part i of the impellingdevice and a ball thrust bearing I3 is inserted between the front faceof he flange H and the rear face of a flange I4 keyed on to the sleeve Iand abutting against the rear face of a collar l on that sleeve. In thisway the unsymmetrical part of the casing, i. e. the part to the rear ofthe flange II is relieved of any thrust exerted by the rotating part ofthe impelling device. The unsymmetrical part of the casing is relievedof thrust exerted by the inner fixed member 8 by anchoring itlongitudinally to the rotating member I instead of to the rear wall I5of the casing. This is done by securing to the rear face of the drivingwheel I2 a tubular member ll supported in a cylindrical bearing I8formed in the rear end of the casing and by inserting a thrust bearingI9 between the front face of an inwardly extending flange 20 at the rearend of the tubular member I! and the rear face of a flange 2| keyed onto the rear end of the stationary member 8 and held in position by thenut 22. The driving wheel I2 is positively secured against the tendencyto rearward movement in an axial direction by a collar 23 screwed on tothe rear end of the rotating part I and the inner concentric part 8 isanchored against rotation by being loosely keyed or loosely splined tothe rear wall I6 of the casing as shown at 25. With the arrangementabove described the thrust on the stationary member 8 is transferredthrough the flange 2I, tube I'I, wheel I2 and collar 23 to the rotatingtube l and through this tube, collar I5, flange I4 and bearing I3 to theinwardly extending flange II on the casing, the thrust exerted directlyon the rotating member is transferred through collar I5, flange I l andbearing I3 to the flange II also, and the thrust on the front end wall 5is transferred to the casing through the nut 25. Consequently the onlypart of the casing subjected to stresses due to the thrust loads is theflange II and the part lying in front of the flange II. This part of thecasing and all the other parts of the machine by which the variousthrust loads are transferred to this part of the casing are tubularmembers of circular cross-section and consequently do not distortasymmetrically under the thrust load. The driving wheel I2 is in theform of an externally toothed gear wheel and the part of the casing tothe rear of the flange II is not symmetrical but is extended downwardsto form a support 26 in the form of a hollow pedestal in which isrotatably mounted a driving shaft 21 carrying a gear wheel 28 whichengages with the teeth of the wheel I2. It will be seen that the casing2 is divided transversely into four parts 2a, 2b, 2c and 2d in order tofacilitate assembly of the machine, These parts are secured together bythe bolts 29.

The arrangement shown in Figures 1 and 2 does not however avoidtemperature stresses, asymmetrical driving stresses and unequalextrusion due to unequal cooling. To avoid these disadvantages there isprovided a modified form of construction which is shown in Figures 3, 4and 5 of the drawings to which reference will now be made. In this formof construction the part of the machine to the front end of the flange II is similar in all material respects to the corresponding part of themachine shown in Figures l and 2 but the externally toothed drivingwheel I2 of the previously described machine is replaced by a drivingwheel M in the form of a flanged collar, the rear end wall of the part2d of the casing is omitted and a drive applied to the inwardlyextending flange 20 on the tubular member I7 secured to the rear face ofthe driving wheel 3! by bolts 32. This permits the parts 20 and 2d ofthe casing to be of circular cross-section throughout, since no openingin the circumferential wall thereof is required in order to permit ofthe application of a drive. The casing is then supported in a pair ofcradles 33 which are heat insulated fro-m the casing, for instance, byinsertions 34 of asbestos material or the like. The tubular member llforming a torque tube is driven by a second driving wheel 35 housed in acylindrical casing 36 and rotatably mounted on a stub shaft 31projecting from the end wall 38 of the casing. The wheel 35 and itscasing are supported by a pedestal 39 in such a manner that the axis ofrotation of the wheel 35 is coincident with that of the extrusionmachine. The wheel 35 is coupled to the torque tube I! by a flexiblecoupling constituted by pins 40 which project from the rear face of theflange 20 and enter rubber lined recesses 4! in the adjacent face of thewheel. Rotation is imparted to the wheel 35 by means of a pinion 42driven from a suitable gear box which is not shown. Rotation of themember 8 carrying the inner die is prevented by loosely splining itsrear end to the hollow stub shaft 3! which is positively secured to theend wall of the gear casing by screws. The machine casing 2 of which thepart 20. forms the stationary part of the impelling device is positivelyheld against rotation by providing on the rear extremity of thecylindrical wall of the part 2d a series of dogs 45 which engage withcorresponding dogs 44 on the adjacent fixed wall of the casing 35.Preferably actual metallic contact of the machine casing 2 and thesecond driving wheel casing 56 is prevented by the interpolation of heatinsulating pads 45 between the engaging surfacesof the dogs.Alternatively, as shown in Figure 6, the machine casing 201 may berestrained from rotating by a series of pegs 46 which project from thefront end face 41 of the casing 36 and enter holes 48 in an outwardlyturned flange 49 on the casing 201. The holes-arelined with heatinsulating material 50 and heat insulating pads 45 are placed betweenthe adjacent surfaces of the two casings.

In the extrusion machine which is shown in Figures 7, 8 and 9 of thedrawings, the screw thread impelling device comprises two longitudinallyextending concentric members, 5Iand 52, having helically extending ribs53 on their adjacent surfaces, the ribs on the one member being ofopposite hand to those on the other. The inner member 5 I is stationaryand the outer member 52 isrotatably driven by means of a driving wheel54 mounted on the rear end of a sleeve member 55 which in turn ismounted on the member 52. The'rotating parts 52, 54 and 55 are supportedin bearings in a frame or casing 55. At its rear end the rotating sleeve52 enters the stationary wall'5'l of the feed chamber 58 formed in theback cover member 59, a sealing gland 60 being provided between the wallof the feed chamber and the rotating sleeve 52. At its front end thesleeve 52 makes a running joint M with the stationary wall 52 on thefront cover 53 in which the extrusion chamber 64 is formed. The innerstationary member 5I extends rearwardly through the feed chamber 58 andis secured to the rear Wall 65 thereof and extends forwardly into theextrusion chamber 64 and is supported at its front end by pads 66constituted by the front extremities of the helical ribs 53 provided onthe outer surface of the member. When the machine is to be used for theproduction of tubing the front end of the stationary member 5I carriesan inner die 67 which co-o-perates with an outer die 58 in the frontwall of the extrusion chamber to form an annular extrusion orifice.Molten metal is fed continuously into feed chamber 58 from whence itflows into the space between the members 5I and 52 where it is cooled sothat it acquires suflicient rigidity to co-operate with the surface ofthe concentric members and be driven forward by them into the extrusionchamber 54 and out through the extrusion orifice. The

thrust exerted on the inner member 5i is transferred directly to theback cover 59 and the thrust exerted on the rotating member 52 istransferred to the frame 56 through the sleeve 55 and the bearing 59inserted between an outwardly extending flange I9 on the sleeve 55 andan inwardly extending flange Ii on the frame 56. An example of a machineof this type is described in the specification of U. S. Patent No.2,051,688.

Hitherto in machines of the kind described in the preceding paragraph,the frame 55 has not been made symmetrical but has been extendeddownwards to form a support in the form of a hollow pedestal in whichare housed a pair of gear wheels by which the drive is imparted to thewheel 54. In the improved construction of machine shown in Figures 7 and8 of the drawings, all parts of the casing subjected to thrust loads areof symmetrical form, the central portion 56 which carries thrust loadsexerted by the plastic metal on the impelling device and in which thedriving wheel 54 is housed being of circular cross-section except forthe provision of two small pockets I2 located adjacent the periphery ofthe driving wheel and on diametrically opposite sides thereof. Thesepockets I2 each house a gear wheel I3 mounted on a shaft 74 supported inbearings I5 in the walls of the pocket. The shafts I4 extend through therear walls of the pockets and are driven through flexible couplings I6and a gear box 92, which is located clear of the machine casing, by asingle driving shaft 1'! which is capable of a limited movement in avertical direction. In the plan view of the gear box one of the twocovers 91 and part of the other cover and also parts of the gearing havebeen removed to expose the interior of the gear box. The gear box 92,comprises a pinion '28 which is mounted on the driving shaft 1'! andengages two spur wheels 19 each of which in turn drives through aco-axial pinion Bil and a spur wheel SI, which is loosely mounted on theshaft 93 as shown in Figure 9, a spur wheel 82 on the shaft 83 to whichthe shaft i is coupled. This arrangement gives a balanced drive. Theextrusion machine itself is supported on feet 84 which extendhorizontally from the side walls of the two pockets "F2 in the machinecasing. As will be seen from Figure 8 these feet are symmetrical about ahorizontal plane containing the machine axis. This symmetrical form ofeasing avoids unsymmetrical distortion thereof due to the thrust load,which distortion would cause mis-alignment of the several bearings andheavy wear on the gland G0 and other bearing surfaces. Preferably heatinsulation 35 is inserted between each supporting foot and the pedestal86 on which the foot rests and the bolts 8'! by which the frame issecured to the pedestal 86 are also heat insulated by insulation 88.Heat insulation 39 is also preferably inserted between the two parts ofthe flexible coupling and between the coupling bolts 98 and the parts inengagement therewith. By this means unsymmetrical cooling of the casingof the machine is reduced and hence the tendency for it to distort undertemperature stresses. The provision of the heat insulation also reducesunsymmetrical cooling of the outer wall of the extrusion chamber.

It will be appreciated that the machine shown in Figures 3-5 of thedrawings may be supported by symmetrically formed feet of the typedescribed in the preceding paragraph instead of by one or more cradles.In this case the need for a positive coupling between the machine casingand the gear casing is avoided.

What I claim as my invention is:

1. In a horizontal metal extrusion machine comprising a screw threadimpelling device, consisting of an inner member and a tubular outermember, by which the metal to be extruded is driven forward in a plasticstate, a driving wheel on one of the members of the impelling device,and a casing housing the impelling device and said driving wheel, theparts of said casing that are subjected to thrust loads exerted by theplastic metal being symmetrical about the axis of the impelling device.

2. In a horizontal metal extrusion machine comprising a screw threadimpelling device, consisting of an inner member and a tubular outermember, by which the metal to be extruded is driven forward in a plasticstate, a machine casing which houses the impelling device and a drivingwheel therefor mounted on one of the members thereof and which issymmetrical about the axis of the impelling device throughout itslength, and means for applying a drive to the driving wheel of theimpelling device through an aperture in the rear end of said casing.

3. In a horizontal metal extrusion machine comprising a screw threadimpelling device, consisting of an inner member and a tubular outermember. by which the metal to be extruded is driven forward in theplastic state, a machine casing which houses the impelling device and adriving wheel therefor mounted on one of the members thereof and whichis symmetrical about the axis of the impelling device throughout itslength, a second driving wheel which is located outside said machinecasing and supported inde pendently thereof and is concentric with thedriving wheel within the casing, and means passing through an aperturein the rear end of said machine casing for coupling together theinternal and external driving wheels.

4. In a horizontal metal extrusion machine comprising a screw threadimpelling device, consisting of an inner member and a tubular outermember, by which the metal to be extruded is driven forward in a plasticstate, a machine casing which houses the impelling device and a drivingwheel therefor mounted on one of the members thereof and whichthroughout its length is symmetrical about the axis of the impellingdevice and also symmetrical in section in any plane containing the saidaxis, and means for applying a drive to the driving wheel of theimpelling device through an aperture in the rear end of said casing.

5. In horizontal metal extrusion machine comprising a screw threadimpelling device, consisting of an inner member and a tubular outermember, by which the metal to be extruded is driven forward in a plasticstate, a machine casing which houses the impelling device and a drivingwheel therefor mounted on one of the members thereof and whichthroughout its length is symmetrical about the th s of the impellingdevice and also symmetrical in section in any plane containing the said6. In a horizontal metal extrusion machine comprising a screw threadimpelling device, consisting of an inner member and a tubular outermember, by which the metal to be extruded is driven forward in a plasticstate, a machine casing which houses the impelling device and a drivingwheel therefor mounted on one of the members thereof and which is ofsubstantially circular cross-section throughout its length and isapertured at its rear end, means for applying a drive to the drivingwheel of the impelling device through the aperture in the rear end ofsaid. casing, and at least one separate supporting cradle for supportingsaid casing.

7. In a horizontal metal extrusion machine comprising a screw threadimpelling device. consisting of an inner member and a tubular outermember, by which the metal to be extruded is driven forward in a plasticstate, a machine casing which houses the impelling device and a drivingwheel therefor mounted on one of the members thereof and which is ofsubstantially circular cross-section throughout its length and isapertured at its rear end, means for applying a drive to the drivingwheel of the impelling device through the aperture in the rear end ofsaid casing, at least one separate supporting cradle for supporting saidcasing, and heat insulation interposed between said casing and saidsupporting cradle.

8. In a horizontal metal extrusion machine comprising a casing whichhouses or forms part of a rotating screw thread impelling device,comprising a rotatably driven inner member and a stationary tubularouter member, by which the metal to be extruded is driven forward in aplastic state, a driving wheel on the driven inner member, means forimparting rotary movement to said driving wheel through anaperture inthe casing, a flange located adjacent the driving wheel and extendinginwardly from the casing, and means for transferring the axial thrustexerted on the driven inner member by the plastic metal to said flangeon the casing, the-part of the casing in front of the said flange beingsymmetrical about the axis of the impelling device.

9. In a horizontal metal extrusion machine comprising a casing whichhouses or forms part of a rotating screw thread impelling device,comprising a rotatably driven inner member and a stationary tubularouter member, by which the metal to be extruded is driven forward in aplastic state, a driving wheel on the driven inner member, means forimparting rotary movement to said driving wheel through an aperture inthe casing, a flange located adjacent the driving wheel and extendinginwardly from the casing, and means for transferring the axial thrustexerted on the driven inner member by the plastic metal to said flangeon the casing, the part of the casing in front of the said flange beingof substantially circular cross-section.

10. In a horizontal metal extrusion machine comprising a casing whichhouses or forms part of a rotating screw thread impelling device,comprising a rotatably driven inner member and a stationary tubularouter member, by which the metal to be extruded is driven forward in aplas tic state, a driving wheel on the driven inner member, means forimparting rotary movement to said driving wheel through an aperture inthe casing, a flange located in front of the driving wheel and extendinginwardly from the casing, and means for transferring the axial thrustexerted on the driven inner member by the plastic metal to said flangeon the casing, the part of the casing in front of the said flange beingof substantially circular cross-section.

11. In a horizontal metal extrusion machine comprising a casing whichhouses or forms part of a rotating screw thread impelling device, comprising a rotatably driven inner member and a stationary tubular outermember, for driving plastic metal forward into an extrusion chamber andout through an annular extrusion orifice formed by inner and outer dies,a support for the inner die. means for transferring the thrust on theinner die and its support to the rotatably driven inner member, adriving wheel on the driven inner member, means for applying rotarymovement to said driving wheel throu h an aperture in the casing, aflange located adjacent said driving wheel and extending inwardl fromthe casing, and means for transferrin the thrust on the driven innermember to said flange, the part of the casing in front of said flangebein f substantially circular cross-section.

12. In a horizontal metal extrusion machine comprising a casing whichhouses or forms, part of a rotating screw thread impelling device,comprising a rotatably driven inner member and a stationary tubularouter member, for driving plastic metal forward into an extrusionchamber and out through an annular extrusion orifice formed by inner andouter dies, a support for the imier die, means for transferring thethrust on the inner die and its support to therotatably driven innermember, a driving wheel on the driven inner member, means for applyingrotary movement to said driving wheel through an aperture in the casing,a flange located in frontof said driving wheel and extending inwardlyfrom the casing, and means for transferring the thrust on the driveninner member to said flange, the part of the casing in front of saidflange being of substantially circular cross-section.

13. In a horizontal metal extrusion machine comprising a casing whichhouses or forms part of a screw thread impelling device constituted byinner and outer concentric tubular members of which the inner is drivenin rotation and by which plastic metal is driven forward and through anannular extrusion orifice constituted by inner and outer dies, a supportfor the inner d e extending rearwardly of the driven inner member, aflange on a part of said support extending beyond the driven member, adriving wheel mounted on the driven inner member, means for applyingrotary movement to said driving wheel through an aperture in the casing,a tubular member secured to the rear face of said driving wheel, aninwardly extending flange on said tubular member, a thrust bearinginterposed between said flange on said support and said inwardlyextending flange, an inwardly extending flange on the casing adjacentthe driving wheel and means for transferring the axial thrust exerted onthe driven inner member by the plastic metal to the said flange on thecasing, the part of the casing in front of the said flange on thetcasing being of substantially circular cross-secion.

14. In a horizontal metal extrusion machine comprising a casing whichhouses or forms part of a screw thread impelling device constituted byinner and outer concentric tubular members of which the inner is drivenin rotation and by which plastic metal is driven forward and through anannular extrusion orifice constituted by inner and outer dies, a supportfor the inner die extending rearwardly of the driven inner member, aflange on a part of said support extending beyond the driven member,. adriving wheel mounted on the driven inner member, means for applyingrotary movement to said driving wheel through an aperture in the casing,a tubular member secured to the rear face of said driving wheel, aninwardly extending flange on said tubular member, a thrust bearinginterposed between said flange on said support and said inwardlyextending flange, a flange on the driven member located in front of saiddriving wheel, an inwardly extending flange on the casing locatedbetween said driving wheel and said flange on the driven member, and athrust bearing interposed between said flange on the casing and saidflange on the driven member, the part of the casing in front of the saidflange on the casing being of substantially circular cross-section.

15. In a horizontal extrusion machine comprising a casing which housesor forms part of a rotating screw thread impelling device, comprising aninner member and a tubular outer member, by which the metal to beextruded is driven forward in a plastic state, a driving wheel on one ofthe members constituting the impelling device, means for impartingrotary movement to said driving wheel through an aperture in the casing,a flange located adjacent the driving wheel and extending inwardly from.the casing, and means for transferring the axial thrust exerted on thedriven member by the plastic metal to said flange on the casing, thepart of the easing in front of said flange and the part housing saiddriving wheel being symmetrical about the machine axis.

16. In a horizontal metal extrusion machine comprising a casing ofsubstantially circular cross-section which houses or forms part of ascrew thread impelling device constituted by inner and outer concentrictubular members of which the inner is driven in rotation and by whichthe plastic metal is driven forward and through an annular extrusionorifice constituted by inner and outer dies, a support for the inner dieextending rearwardly of the driven inner member, a driving wheel mountedon the driven inner member, a torque tube coupled to said driving wheeland extending rearwardly thereof, means for applying through an aperturein the rear end of the machine casing, a drive to the rear end of saidtorque tube, an inwardly extending flange on said torque tube, anoutwardly extending flange on a part of said inner die support extendingbeyond the driven member, a thrust bearing interposed between saidinwardly extending flange and said outwardly extending flange, aninwardly extending flange on the casing adjacent the driving wheel andmeans for transferring the axial thrust exerted on the driven innermembar to the said flange on the casing.

1'7. In a horizontal metal extrusion machine comprising a casing ofcircular cross-section which houses or forms part of a screw threadimpelling device constituted by inner and outer concentric tubularmembers of which the inner is driven in rotation and by which theplastic metal is driven forward and through an annular e};- trusionorifice constituted by inner and outer dies, a support for the inner dieextending rearwardly of the driven inner member, a driving wheel mountedon the driven inner member, a torque tube coupled to said driving wheeland extending rearwardly thereof, means for applying through an aperturein the rear end of the machine casing, a drive to the rear end of saidtorque tube, an inwardly extending flange on said torque tube, anoutwardly extending flange on a part of said inner die support extendingbeyond the driven member, a thrust bearing interposed between saidinwardly extending flange and said outwardly extending flange, a flangeon the driven member, an inwardly extending flange on the casing locatedbetween the driving wheel and the flange on the driven member, and athrust bearing interposed between said flange on the driven member andsaid flange on the casing.

18. In a metal extrusion machine as specified in claim 16, at least onecradle for supporting the machine casing, a second driving wheel locatedto the rear of the extrusion machine casing and supported independentlythereof, a flexible coupling between said second driving wheel and saidtorque tube, a casing for said second driving wheel, means comprisinginterengaging surfaces on said second driving wheel casing and themachine casing, for positively restraining the machine casing fromrotating in said cradle.

19. In a metal extrusion machine as specified in claim 16, at least onecradle for supporting the machine casing, a second driving wheel locatedto the rear of the extrusion machine casing, supported independentlythereof and coaxial therewith, flexible coupling between said seconddriving wheel and said torque tube, a casing for said second drivingwheel, and means for coupling said second driving wheel casing to saidmachine casing whereby positively to restrain said machine casing fromrotating in said cradle, said coupling means comprising projections onone of said casings and recesses on the other of said casings and heatinsulating material interpolated between said projections and recesseswhereby to prevent metallic contact between said casings.

20. In a horizontal metal extrusion machine comprising a screw threadimpelling device, consisting of an inner member and a rotatable tubularouter member, by which plastic metal is driven forward and through anextrusion orifice, a driving wheel carried by the rotatable outermember, a machine casing comprising a central I portion housing saiddriving wheel and subjected to thrust loads exerted by the plasticmetal, said central portion being of circular cross-section except forthe provision therein of two pockets lo cated on diametrically oppositesides of said central portion, a pair of gear wheels housed one in eachpocket in said casing and in engagement with said driving wheel, andmeans for driving each of said gear wheels.

21. In a horizontal metal extrusion machine comprising a screw threadimpelling device, consisting of an inner member and a rotatable tubularouter member, by which plastic metal is driven forward and through anextrusion orifice, a driving wheel carried by the rotatable outermember, a machine casing comprising a central portion housing saiddriving wheel and carrying thrust loads exerted by the plastic metal onthe impelling device, said central portion being of circularcross-section except for the provision therein of two pockets located ondiametrically opposite sides of said central portion, a gear wheelhoused in each pocket and engaging said driving wheel, means for drivingeach of said gear wheels, supporting feet extending one from the wall ofeach pocket in the central portion of the said machine casing, saidpockets and said feet being symmetrical about a horizontal planecontaining the machine axis.

22'. In a horizontal metal extrusion machine comprising a screw threadimpelling device. consisting of an inner member and a rotatable tubu--lar outer member. by which plastic metal is driven forward through anextrusion orifice, a driving wheel carried by the rotatable outermember, a machine casing comprising a central. portion housing saiddriving wheel and carrying thrust loads exerted by the plastic metal onthe ill)- pelling device, said central portion being of circularcross-section except for the provision therein of two pockets located ondiametrically opposite sides of the central portion. a pair of gearwheels housed one in each pocket and engaging said driving wheel, a pairof shafts supporting said gear wheels and extending through the walls ofthe pockets, means for driving each of said shafts, heat insulatingmaterial inserted between said shafts and said driving means, supportingfeet which extend one from the wall of each pocket in the said machinecasing, said supporting feet and pockets being symmetrical about ahorizontal plane containing the machine axis. a pedestal for eachsupporting foot, and heat insulating material inserted between eachsupporting foot and its pedestal.

23. In a horizontal metal extrusion machine with a screw threadimpelling device, comprising a rotatably driven tubular member withinwhich is located a stationary member carrying an inner die at its frontend past which the metal to be extruded is driven forward in a plasticstate, a machine casing housing the impelling device and a driving wheeltherefor on the rotatably driven tubular member, means for transferringto the said casing the axial thrust exerted on the driven member by theplastic metal and the axial thrust exerted on the said Stationarydie-carrying memher by the plastic metal, the part of said casing infront of the point at which the thrust on the stationary die-carryingmember is transferred to the casing being symmetrical about the axis ofthe impelling device.

24. In a horizontal metal extrusion machine with a screw threadimpelling device comprising a rotatably driven tubular member withinwhich is located a stationary member carrying an inner die at its frontend past which the metal to be extruded is driven forward in a plasticstate, a machine casing housing the impelling device and a driving wheeltherefor on the rotatably driven tubular member, means fortransferring'to the said casing the axial thrust exerted on the drivenmember by the plastic metal and the axial thrust exerted on the saidstationary die-carrying member by the plastic metal, the part of saidcasing in front of the point at which the thrust on the stationarydie-carrying member is transferred to the casing being symmetrical aboutthe axis of the impelling device and also symmetrical in section in anyplane containing the said axis.

GEORGE THOMAS WILSON GRIEVE.

